Reed switch cartridge

ABSTRACT

A reed switch cartridge is attached for operation by an oil tight switch actuator and is interchangeable with conventional switch cartridges. Two embodiments are shown and each includes a pair of reed switches which are positioned in switch chambers located on opposite sides of a plunger. A magnet carried by the plunger is polarized in the direction of plunger motion and generates a concentrated magnetic field at each of its ends. By operating the reed switches off the ends of the magnet a minimum amount of space is required for the switch-magnet combinations and changes in &#39;&#39;&#39;&#39;pick-up&#39;&#39;&#39;&#39; and &#39;&#39;&#39;&#39;drop-out&#39;&#39;&#39;&#39; points are minimized despite possible variations in magnet length or flux density. Means including clips are shown for adjusting the position of each reed switch and for thereby adjusting their initial pick-up and drop-out points.

United States Patent 1 Funke 11 3,745,493 July 10, 1973 REED SWITCHCARTRIDGE {75 l Inventor: Richard A. Funke, New Berlin,

Wis.

[73 I Assignee: Allen Bradley Company, Milwaukee,

Wis.

[22] Filed: Sept. 1, 1972 [21] Appl. No.: 285,720

Primary Examiner-Roy N. Envall, Jr. AttorneyBarry E. Sammons et al.

[57] ABSTRACT A reed switch cartridge is attached for operation by anoil tight switch actuator and is interchangeable with conventionalswitch cartridges. Two embodiments are shown and each includes a pair ofreed switches which are positioned in switch chambers located onopposite sides of a plunger. A magnet carried by the plunger ispolarized in the direction of plunger motion and generates aconcentrated magnetic field at each of its ends. By operating the reedswitches off the ends of the magnet a minimum amount of space isrequired for the switch-magnet combinations and changes in pick-up" anddrop-out points are minimized despite possible variations in magnetlength or flux density. Means including clips are shown for adjustingthe position of each reed switch and for thereby adjusting their initialpick-up and drop-out points.

12 Claims, 7 Drawing Figures PATENIEBJUL 1 man 745,493

SHEET 1 BF 3 1 REED SWITCH CARTRIDGE BACKGROUND OF THE INVENTION Theinvention relates to control switches, and more particularly, toswitches of the rotary selector and pushbutton type which are commonlyattached to the enclosure of such electrical equipment as motorstarters, motor speed control circuits, and numerical control directors.

With the increased use of low voltage logic circuits at the input toelectrical equipment, the demand for switches containing hermeticallysealed, magnetically operable contacts, has increased dramatically. Sucha switch, commonly referred to as a reed switch, is illustrated in US.Pat. No. 3,243,544, issued to J.C. Mayer on Mar. 29, 1966.

There are numerous commercially available oil-tight switches whichcontain Ser. No. 275,602 filed July 27, 1972 and entitled SwitchMounting Structure, such switches include an actuator section of eitherthe pushbutton or rotary selector type, and a contact block sectionwhich contains one or more switch cartridges. The switch cartridges aremodular in construction, that is, they can be easily removed from theactuator section and replaced with other similar cartridges. In additionto having similar physical shapes and dimensions, each cartridgeincludes a plunger which extends into the actuator section of the switchand is operated by the mechanism therein to open and close one or moreswitch contacts in the cartridge. To provide a truly module switchcartridge, not only must the shape and dimensions of the switchcartridge be compatible, but a uniform plunger stroke must also bespecified.

To provide a reed switch cartridge which is truly interchangeable withconventional switch cartridges, its shape, size and plunger stroke mustbe constrained in order to operate properly with commerically availableswitch actuators. The limited cartridge size and short and preciseplunger stroke requirements associated with such switch actuators hasheretofore proven to be a difficult constraint on the design ofmagnetically operated reed switch cartridges.

SUMMARY OF THE INVENTION The present invention relates to a means ofoperating reed switches, and more specifically to a reed switchcartridge which is compatible with actuators used to operateconventional switches. The reed switch cartridge includes a frame thatdefines a switch chamber, a plunger slidably retained to the frame fortranslational motion along a central axis located adjacent to the switchchamber, a reed switch located in the switch chamber with its lengthwisedimension oriented substantially parallel to the central axis, and amagnet having a lengthwise dimension and a lateral dimension, whichmagnet is polarized along its lateral dimension and which is connectedto the plunger with its lengthwise dimension oriented perpendicular tothe central axis. A high energy ferrite magnet is used and the magneticfield which it generates is concentrated at its end positionedimmediately adjacent the reed switch. Operation of the reed switch isthus accomplished in a minimum amount of space and the pick-up anddrop-out points are precisely defined with respect to the leading edgeof the magnet.

A general object of the invention is to provide a reed switch cartridgewhich is compatible with existing switch actuators. By operating thereed switch off the end of a high energy magnet, the pick-up and dropoutpoints are made compatible with the plunger stroke requirements ofexisting switch actuators. Two reed switches may be operated in thismanner, one off each end of the magnet.

A more specific object of the invention is to provide a reed switchcartridge in which either normally open or normally closed operation canbe obtained. An offset gap reed switch is used, and by orienting theswitch in the switch chamber in one direction a normally open operationis obtained. By orienting it in the opposite direction, a normallyclosed operation is obtained.

Another object of the invention is to provide a reed switch cartridgewhich is easily assembled and adjusted. The reed switches are retainedto the cartridge frame by means of clips which allow adjustment of theirposition along an axis parallel to the central axis. Despite variationsin magnet strength and reed switch operating characteristics, theposition of the switches may be adjusted to pick up and drop out at thedesired plunger position. Once the desired position is established, thereed switches are bonded in place.

The foregoing and other objects and advantages of the invention willappear from the following drawings which form a part hereof and whichshow by way of illustration two preferred embodiments of the invention.Such embodiments do not necessarily represent the full scope of theinvention, and reference is made to the claims herein for interpretingthe breadth of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in cross section ofthe reed switch cartridge connected to a pushbutton type switchactuator,

FIG. 2 is a view in cross section of the switch of FIG. 1 taken alongthe plane 2-2,

FIG. 3 is a perspective view of the plunger and magnet which forms apart of the reed switch cartridge of FIG. 1,

FIG. 4 is a plan view of a selector switch containing a secondembodiment of the invention,

FIG. 5 is a perspective view of one of the two reed switch cartridgescontained in the selector switch of FIG. 4,

FIG. 6 is a plan view with parts cut away of the reed switch cartridgeof FIG. 5, and

FIG. 7 is a schematic drawing of the magnet which is used in bothembodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, anoil-tight switch includes an actuator 1 and a contact block 2. Theactuator l includes a pushbutton mechanism 3 which is connected forreciprocating motion in a central opening 4 of an actuator sleeve 5. Theactuator 1 also includes a rectangular bearing plate 6 which isintegrally formed to the actuator sleeve 5 and which extends radiallyoutward therefrom to form'a clamping surface 7. A set of four rubbergaskets 8 are disposed around the actuator sleeve 5 and positionedbetween the clamping surface 7 and the back surface of a mounting wall9. The actuator sleeve 5 extends through an opening in the mounting wall9 and a cover 10 is disposed around its forward end to enclose thepushbutton mechanism 3 and fasten the actuator sleeve 5 to the mountingwall 9. For a detailed description of the actuator section 1 andparticularly the manner in which it is attached to the mounting wall 9,reference is made to a copending patent application Ser. No. 270,420,filed July 10, 1972 and entitled Switch Mounting Structure.

The contact block 2 is attached to the actuator 1 by means of four bolts(not shown in the drawings) which extend through the rectangular bearingplate 6 into threaded openings formed in the contact block framework 11.Securely fastened to the framework 11 is a switch cartridge whichincludes a frame 12 formed from a molded polyphenylene oxide plastic todefine a pair of switch chambers 13a and 13b. The frame 12 includes abottom wall 14, a pair of side walls 15a and 15b which extend upwardfrom opposing edges of the bottom wall 14, and a front wall 16 whichextends upward from the bottom wall 14 to join the forward ends of theside walls 15a and 15b. Disposed along the back edge of the bottom wall14, and joining the back end of the side walls 15a and 15b are two setsof terminal chambers 17 and 18, one set associated with each switchchamber 13a and 13b.

The first set of terminal chambers 17 is defined by three integrallyformed walls; an outside wall 19a which extends parallel to the sidewall 15a but is disposed laterally outward therefrom, a partition adisposed laterally inward from the outside wall 19a, and an interiorwall 22a disposed laterally inward from the partition 20a and extendingin a direction parallel thereto to define a second terminal chamber 23a.The second terminal chamber set 18 is a mirror image of the terminalchamber set 17 and includes an outside wall 19b, a partition 20b and aninterior wall 22b which define a third terminal chamber 21b and a fourthterminal chamber 23b. A set of four brass terminals 24-27 are fastenedto the cartridge bottom wall 14 and located in the respective lugchambers 21a, 23a, 23b and 21b.

The switch cartridge is symmetrical about a central, longitudinal axis28 which extends rearward through a central opening 29 in the front wall16, between the switch chambers 13a and 13b, and between the terminalchamber sets 17 and 18. A plunger 30 is disposed along the central axis28 and is slidably retained to operate along the central axis 28 by twosets of opposing retainer walls 31a and 31b. The retainer walls 31a and31b are integrally formed to, and extend upward from, the bottom wall14.

Referring to FIGS. 1 and 3, the plunger 30 includes a substantiallyrectangular-shaped magnet carrier por tion 32 and an integrally formedoperating end 33. The magnet carrier 32 is slidably retained between theretainer walls 31a and 31b and the operating end 33 extends from itsforward end, through the central opening 29 in the front wall 16, andinto the actuator section 1. The plunger 30 is biased in a forward, orunactuated position, by a bias spring 34 which is disposed between theback end of the magnet-carrier 32 and a web 35 which bridges between theinterior walls 22a and 22b. The plunger 30 is formed of moldedacetalplastic and the magnet carrier portion 32 has a pair of slots 36which are'formed in opposing walls thereof and which extend from itsback end, forward approximately two thirds of its length. A pair ofopposing fingers 37 are formed along the edges of each slot 36, and eachfinger 36 is formed a flex inward towards one another to provide aslight constriction in the width of each slot 36 near its forward end. Arectangular-shaped magnet 38 is inserted into the slots 36 and is wedgedbetween the fingers 37 which retain it to the carrier 32. The magnet 38is a high energy magnet made from a ferrite material designed M-S whichis commercially available from the Allen-Bradley Company. The magnet 38has a re sidual flux density of approximately 3,800 gauss and a coerciveforce of approximately 2,500 orsteds.

Referring to FIGS. 1 and 7, the magnet 38 has a longitudinal dimensionwhich is co-linear with an axis 39, and lateral dimensions which areco-linear with orthogonal axes 40 and 41. The magnet 38 is polarized inthe direction of the orthogonal axis 40, or in other words along one ofits lateral dimensions, and the resulting field is concentrated at eachof its ends as indicated by the dashed lines 42 and 43. The magnet 38is-positioned in the switch cartridge with its lengthwise axis 39perpendicuar to the central axis 28 of the switch cartridge. The ends ofthe magnet 38 thus extend laterally away from the central axis 28 andare located immediately adjacent the switch chambers 13a and 13b. As aresult, when the plunger 30 is operated, the magnet 38 is translatedalong the central axis 28 and the concentrated magnetic field at each ofits ends is moved along the length of the switch chambers 13a and 13b.

Located in the respective switch chambers 13a and 13b are a pair of reedswitches 44 and 45. The reed switches 44 and 45 are commerciallyavailable miniature offset-gap switches having an ampere-turn pick-upranging from 25 to 40. The first reed switch 44 is connected to theswitch cartridge by a pair of molded polycarbonate plastic clips 46 and47 which are rigidly fastened to and extend upward from the bottom wall14 of the frame 12. The switch leads are snapped into a slot formed inthe top surface of each of the clips 46 and 47, and the reed switch 44is thus slidably retained to the switch cartridge. An adjustment opening48 is formed in the forward wall 16 of the frame 12 immediately forwardof the reed switch 44, and by inserting a tool through this opening, thelongitudinal position of the reed switch 44 can be adjusted after thecartridge is completely assembled. The second reed switch 45 issimilarly mounted to the frame 12 by a pair of clips 49 and 50, and asecond adjustment opening 51 is formed in the front wall 16 immediatelyforward of it.

The leads on the" reed switch 44 are connected to the larly, the leadson the second reed switch 45.are connected through respective conductors55 and 56 to the lugs 27 and;26, and a divider wall 57 is formed in theswitch chamber 15b between them.

Referring to FIG. 1, the first reed switch 44 is positioned in theswitch cartridge with its offset gap located toward the forward end ofthe cartridge. On the other hand, the second reed switch 45 is orientedwith its offset gap toward the back end of the cartridge. As a result,the reed switch 44 operates as a normally closed switch and the reedswitch 45 operates as a normally open switch. The plunger 30 istranslated from its unactuated position shown in FIG. 1 by depressingthe pushbutton mechanism 3 against the operating end 33 of the plunger30. The plunger is translated one-quarter inch to an actuated positionin which the bias spring 34 is completely compressed. In this actuatedposition, the concentrated magnetic field at each end of the magnet 38is removed from the vicinity of the gap in the first reed switch 44 andinto vicinity of the gap in the second reed switch 45. The specificpoints at which the switches 44 and 45 drop out and pick up varyconsiderably, depending primarily upon the particular magnet and reedswitch chosen. Uniformity of operating characteristics is obtained,however, by adjusting the longitudinal position of the reed switches 44and 45 through the adjusting openings 48 and 51. Once their positionsare established the reed switches 44 and 45 are secured in place with adrop of adhesive on the clips 46 and 47.

In the preferred embodiment of the invention shown in FIGS. 1-3, theposition of the normally closed reed switch 44 is adjusted to open after0.05 inches of plunger travel from its unactuated position. The positionof the normally open reed switch 45 is adjusted to close at a plungerposition of 0.16 inches from the unactuated position. On the returnmotion of the plunger 30, the normally open switch 45 drops out when theplunger is approximately 0.135 inches from the unactuated position andthe normally closed swich 44 picks up at approximately 0.025 inches fromthe unactuated position. A differential of approximately 0.025 inches isthus obtained between the pick-up and drop-out points of each reedswitch 44 and 45. This differential minimizes the possibility ofinadvertently opening and closing the switch during plunger travel.Although a normally open and normally closed pushbutton switchingfunction is performed by the embodiment shown in FIGS. 1-3, it should beapparent to those skilled in the art that a variety of switchingfunctions can be provided merely be reversing the orientation of one orboth of the reed switches 44 and 45.

The second embodiment of the invention shown in FIGS. 4-6 is applied toa selector type switch actuator mechanism. The shape and physicaldimensions of the cartridge differ from that shown and described above,however, the principles of operation are the same and this secondembodiment is intended to illustrate the application of the invention toa different commercially available switch actuator. Referring to FIG. 4,the selector switch includes a selector switch actuator and a contactblock 61. The contact block is comprised of two reed switch cartridges.The switch actuator 60 includes a knob 62, which when rotated, operatesa cam (not shown in the drawings) contained in a cylindrical bodyportion 64 of the switch. Rotation of the cam translates a pair of camfollower elements (also contained within the body portion 64) along acentral switch axis 65 to operate the contacts in the contact block 61.For a more detailed description of the structure and operation of theswitch actuator 60, reference is made to the copending patentapplication Ser. No. 286,531, filed Sept. 5, 1972, and entitledOil-Tight Selector Switch.

The contact block 61 is comprised of two reed switch cartridges, one ofwhich cartridges 66 is shown in the drawings. The cartridge 66 includesa frame 67 which is formed of molded phenolic plastic, and includespolycarbonate plastic cover 68 which has a pair of opposing up-turnedend pieces 69 and 70. Four openings in the cover 68 allow two sets ofterminals 71a, b and 72a, b to extend upward through the cover 68.Threaded openings in each terminal 71a, b and 72a, b receive a screw 73and attached wire clamp 74.

Referring to FIG. 5 in which the cover 68 is removed from the frame 67,a plunger 75 formed from molded acetal plastic and having a generallyrectangular shape is slidably retained to the frame 67 for translationalmovement in a channel 76 located in the plane of the central switch axis65. A bias spring 77 is positioned in the channel between the back endof the plunger 75 and an integrally formed back wall 78. A pair of keys79 and 80 are formed on opposing sides of the plunger 75 and a keyway 81and 82 is formed along each side of the channel 76 to receive therespective keys 79 and 80 and to provide limits on the translationalmotion of the plunger 75. An operating head 83 is formed on the forwardend of the plunger 75 and communicates with one cam follower element inthe switch actuator section 60 through an opening 84 at the forward endof the channel 76. A magnet 85 is inserted through an opening in theplunger 75 in a manner similar to that shown in FIG. 3 and describedabove. The magnet 85 is made of a ferrite material (M-5) and isidentical to the magnet 38 shown in FIG. 7 and described above. Itincludes a longitudinal dimension which is substantially larger than itslateral dimensions and it is polarized in the direction of the centralaxis 65.

The ends of the magnet 85 extend laterally outward a short distance fromthe plunger 75 and into switch chambers 86 and 87 formed in the frame 67along each side of the channel 76. A hermetically sealed reed switch 88is located in the switch chamber 86 and connected to the frame 67 by apair of clips 89 and 90. The base of each clip 89 and 90 is firmlyattached to the frame 67 and the two leads of the reed switch 88 areslidably retained in slots 91 and 92 formed in the top of each. A secondreed switch 93 located in the second switch chamber 87 is similarlyattached to the frame 67 by a pair of clips 94 and 95. A pair ofconductors 96 and 97 connect the leads of the first reed switch 88 tothe respective terminals 71a and 71b, and a pair of conductors 98 and 99connect the leads of the second reed switch 93 to the respectiveterminals 720 and 72b.

The reed switches 88 and 93 are positioned in the respective switchchambers 86 and 87 with their lengthwise dimension parallel to thecentral axis 65. The body portion of each reed switch 88 and 93 ispositioned immediately adjacent one of the ends of the magnet 85 and theoffset gap 100 and 101 in each is oriented towards the back of theswitch cartridge. The end of one lead on the first reed switch 88extends into a forward adjustment opening 102 in the frame 67 and theend of its other lead extends through a back adjustment opening 103.Similarly, the leads of the second switch 93 extend into a forwardadjustment opening 104 and a back adjustment opening 105 to allowadjustment of the longitudinal position of the switch 93 after thecartridge 66 is assembled. After the longitudinal position of each reedswitch 88 and 93 has been adjusted to provide the desired pull-in anddrop-out points, an adhesive is placed in'the slot of the clips 90 and91 to securely fasten the reed switches 88 and 93 to the frame 67.

With a relatively short plunger stroke (0.250 inches) the reed switches88 and 93 are opened and closed by the magnetic field generated at eachend of the magnet 85. A number of factors contribute to the shortenedplunger stroke. These include the relatively small lateral dimension, orwidth, of the magnet 85(0.l30 inches) as compared to the length of thereed switch body (0.520 inches), and the operation of the reed switchoff the end of the magnet 85. The magnetic field is concentrated at theends of the magnet 85 to provide a high gradient which results in largechanges in magnetic flux at the switch gaps 100 and 101 with arelatively short plunger stroke. Sufficient flux is provided to operatethe switches by using a high energy ferrite magnet that is polarized inthe direction of the central axis 65. As in the pushbutton embodimentshown in FIGS. l-3, a variety of switching functions can be providedmerely by reversing the orientation of one or both of the reed switches88 and 93.

Two embodiments of the invented reed switch cartridge have beendescribed and illustrated and it should be apparent that either can beused with pushbutton or selector switch actuators. In each embodiment, amagnet is translated along a switch axis by a plunger and one or morereed switches are positioned along the ends of the magnet. A number offactors contribute to the compact design of both embodiments of theinvention. These include a small switch body size, operating the switchoff the end of the magnet, and a relatively small lateral dimension orthickness of the magnet. As a result, the reed switches need not beoffset along the central switch axis to provide a reasonabledifferential, and the longitudinal dimensions of the switch cartridgeare minimized.

I claim:

1. In a switch including a switch actuator section which is operable totranslate a plunger along a central switch axis, a reed switch cartridgecomprising:

a frame that defines a switch chamber;

a plunger slidably retained to the frame for translational motion alongthe central switch axis and being disposed adjacent said switch chamber;

a reed switch connected to said frame and positioned within said switchchamber with its lengthwise dimension oriented substantially parallel tothe central switch axis; and

a magnet connected to said plunger, said magnet having a lengthwisedimension and a lateral dimension substantially less than saidlengthwise dimension said magnet being oriented with its lengthwisedimension substantially perpendicular to said central switch axis, andsaid magnet being polarized along its lateral dimension;

wherein operation of said switch actuator section translates saidplunger and attached magnet to operate said reed switch.

2. The reed switch cartridge as recited in claim 1 wherein said magnethas a pair of lateral dimensions which define two ends and in which saidreed switch is positioned in said switch chamber immediately adjacentone of said magnet ends.

3. The reed switch cartridge as recited in claim 2 in which said magnetis polarized in the direction of said central switch axis.

4. The reed switch as recited in claim 3 in which a second switchchamber is formed in said frame and a second reed switch is contained insaid second switch chamber to operate off the second end of said magnet.

5. The reed switch cartridge as recited in claim 3 in which the lateraldimension of said magnet in the direction of said central switch axis isless than one third the length dimension of said reed switch body.

6. The reed switch cartridge as recited in claim 3 in which said plungeris operated between an unactuated and actuated position and in which helateral dimension of said magnet in the direction of said central switchaxis is less than one half the plunger stroke.

7. The reed switch cartridge as recited in claim 6 in which said magnetis formed from a ferrite material.

8. The reed switch cartridge as recited in claim 1 in which said reedswitch is connected to said frame by a pair of clips which allow theposition of the reed switch to be adjusted in the direction of thecentral switch axis.

9. The reed switch cartridge as recited in claim 8 in which said reedswitch includes a pair of leads which extend from its ends in thedirection of the central switch axis, in which said clips are rigidlyattached to said frame, and in which said reed switch leads are slidablyretained in slots formed in said clips.

10. The reed switch cartridge as recited in claim 9 in which anadjustment opening is formed in said frame in alignment with one of saidreed switch leads.

11. The reed switch cartridge as recited in claim 1 in which said reedswitch has an offset gap and in which it may be positioned in saidswitch chamber in one direction to obtain a normally open mode ofoperation, or it may be positioned in the reverse direction to obtain anormally closed mode of operation.

12. The reed switch cartridge as recited in claim 1 in which said framedefines a second switch chamber adjacent said plunger and a second reedswitch is connected to said frame and positioned in said second switchchamber with its lengthwise dimension oriented substantially parallel tothe central switch axis, and wherein said first and second reed switchesare in substantial alignment with one another along the central switchaxis.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,745,493 Dated July 10. 1973 Inventor) Richard A. Funke It is certifiedthat error appears in the above-identified patent v and that saidLetters Patent are hereby corrected as shown below:

Column 1 line 18 after contain insert conventional switch contacts. Asdisclosed in the copending patent application Column A, line 5" designedshould be designated Column 5, line 26 1 l swich should be switch Column5, line 37 be should be by Claim 6, line 3 4 he should be the Signed andsealed this 22nd day of January 197L SEAL) Attest:

EDWARD M. FLETCHER, JR. RENE D. TEGTME'YER I Attestlng Officer ActingCommissioner of Patents P0-1050 UNITED STATES PATENT OFFICE (5/69)CERTIFICATE OF CORRECTION" Patent No. 3,745,493 Dated July 10 1973Inventor) Ricbatd A. Funke It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

FT a

Column 1 line 18 after contain insert conventional switch contacts. Asdisclosed in the copending patent application Column 4, line designedshould be designated- Column 5, line 26 n swich should be switch Column5, line 37 I be should be by Claim. 6, line 3 i he should be the Signedand sealed this 22nd day of January 197 i- (SEAL) Attest:

EDWARD M.FLETCHER,JR. RENE D. TEGTME'YER I nAttestlng Officer ActingCommission-er of Patents

1. In a switch including a switch actuator section which is operable totranslate a plunger along a central switch axis, a reed switch cartridgecomprising: a frame that defines a switch chamber; a plunger slidablyretained to the frame for translational motion along the central switchaxis and being disposed adjacent said switch chamber; a reed switchconnected to said frame and positioned within said switch chamber withits lengthwise dimension oriented substantially parallel to the centralswitch axis; and a magnet connected to said plunger, said magnet havinga lengthwise dimension and a lateral dimension substantially less thansaid lengthwise dimension said magnet being oriented with its lengthwisedimension substantially perpendicular to said central switch axis, andsaid magnet being polarized along its lateral dimension; whereinoperation of said switch actuator section translates said plunger andattached magnet to operate said reed switch.
 2. The reed switchcartridge as recited in claim 1 wherein said magnet has a pair oflateral dimensions which define two ends and in which said reed switchis positioned in said switch chamber immediately adjacent one of saidmagnet ends.
 3. The reed switch cartridge as recited in claim 2 in whichsaid magnet is polarized in the direction of said central switch axis.4. The reed switch as recited in claim 3 in which a second switchchamber is formed in said frame and a second reed switch is contained insaid second switch chamber to operate off the second end of said magnet.5. The reed switch cartridge as recited in claim 3 in which the lateraldimension of said magnet in the direction of said central switch axis isless than one third the length dimension of said reed switch body. 6.The reed switch cartridge as recited in claim 3 in which said plunger isoperated between an unactuated and actuated position and in which helateral dimension of said magnet in the direction of said central switchaxis is less than one half the plunger stroke.
 7. The reed switchcartridge as recited in claim 6 in which said magnet is formed from aferrite material.
 8. The reed switch cartridge as recited in claim 1 inwhich said reed switch is connected to said frame by a pair of clipswhich allow the position of the reed switch to be adjusted in thedirection of the central switch axis.
 9. The reed switch cartridge asrecited in claim 8 in which said reed switch includes a pair of leadswhich extend from its ends in the direction of the central switch axis,in which said clips are rigidly attached to said frame, and in whichsaid reed switch leads are slidably retained in slots formed in saidclips.
 10. The reed switch cartridge as recited in claim 9 in which anadjustment opening is formed in said frame in alignment with one of saidreed switch leads.
 11. The reed switch cartridge as recited in claim 1in which said reed switch has an offset gap and in which it may bepositioned in said switch chamber in one direction to obtain a normallyopen mode of operation, or it may be positioned in the reverse directionto obtain a normally closed mode of operation.
 12. The reed switchcartridge as recited in claim 1 in which said frame defines a secondswitch chamber adjacent said plunger and a second reed switch isconnected to said frame and positioned in said second switch chamberwith its lengthwise dimension oriented substantially parallel to thecentral switch axis, and wherein said first and second reed switches arein substantial alignment with one another along the central switch axis.